Rhombohedral and Turbostratic Boron Nitride Polytypes Investigated by X-ray Absorption Spectroscopy

Abstract

The electronic structure of rhombohedral sp2-hybridized boron nitride (r-BN) is characterized by X-ray absorption near-edge structure spectroscopy. Measurements are performed at the boron and nitrogen K-edges (1s) and interpreted with first-principles density functional theory calculations, including final state effects by applying a core hole. We show that it is possible to distinguish between different 2D planar polytypes such as rhombohedral, twinned rhombohedral, hexagonal, and turbostratic BN by the difference in chemical shifts. In particular, the chemical shift at the B 1s-edge is shown to be significant for the turbostratic polytype. This implies that the band gap can be tuned by a superposition of different polytypes and stacking of lattice planes.

Flow Modulation Epitaxy of Thick Boron Nitride Epilayers and Wafer-Level Exfoliation

“…However, the 2θ of h -BN and r -BN are all around 26.7°, indicating some inaccuracies with our sp 2 -BN. When both h -BN and r -BN exist in BN, the 2θ might be around 25–28° . Therefore, our sp 2 -BN belongs to t -BN, which can also be found in Figure c.…”

“…When both h-BN and r-BN exist in BN, the 2θ might be around 25− 28°. 40 Therefore, our sp 2 -BN belongs to t-BN, which can also be found in Figure 3c. Further research is needed to determine how to regulate the crystal structure of sp 2 -BN.…”

Phase Evolution of Boron Nitride and Carbide during Chemical Vapor Deposition

“…Out of the well-ordered sp 2 -hybridised forms of BN, h-BN has attracted the most interest in this research eld while r-BN has received relatively limited attention. One of the reasons for this di erence is due to the di culties associated with material and phase characterisation 7,8 which can be attributed to the similarities in the h-BN and r-BN structures. Both h-BN and r-BN consist of the same 2D honeycomb-shaped basal planes consisting of alternating B and N atoms, but these planes are instead stacked di erently with respect to the layer below, albeit with similar spacing between the basal planes, as illustrated in Figure 2.…”

“…e less-ordered a-BN is a promising ultra-low dielectric material that can, given its mechanical properties, also act as a diffusion barrier. [22][23][24] In the past t-BN was studied to form ordered phases of BN [25][26][27] , recently some characterisation tools have been used to identify more t-BN properties 8,28,29 . In general, given its material properties, t-BN can replace graphite in applications like lubricants and polymer fillers but additionally as insulators, for thermal and protective coatings etc.…”

Polytypism and Packing-Dependent Colossal Positive and Negative Thermal Expansion in a 2D Layered Cerium-Based Coordination Polymer

“…Polytypism is an abundant phenomenon in chemistry and crystallography, which plays an important role in numerous solid-state systems. − In the structure of a compound prone to polytypism, atomic layers or layered structural units may adopt different stacking motifs, thereby yielding two or more crystalline modifications known as polytypes. − For certain systems (e.g., SiC and CdI 2 ), crystallographic data include up to hundreds of polytypes. , The latter differ not only in their crystal structure but also in structure-related physical characteristics (optical properties, − thermal conductivity, , band structure, − crystal “hopping” effect, and even superconductivity) that makes them a versatile platform for the development of functional materials with tunable properties.…”